1. Field of the Invention
The present invention relates to a slurry to be used for CMP (Chemical Mechanical Polishing), a polishing method using the slurry, and a method of manufacturing a semiconductor device.
2. Description of the Related Art
It is expected that the integration of semiconductor elements in high performance LSIs of the next generation would be inevitably further enhanced. For example, the design rule of damascene wirings to be formed by CMP is expected to become so severe that the line width of wirings is confined within the range of 0.07 to 30 μm and the film thickness of wirings is confined to 100 nm or less.
When forming damascene wirings having a film thickness of 100 nm by the conventional CMP, abrasive grains which are detached from a polishing pad during polishing becomes free particles which are subsequently thrust into a surface to be polished (which may be referred hereinafter to “a polishing surface”) to generate erosion having a depth of about 80 nm. In such a case, most of the wiring material (Cu, Al, W, etc.) buried inside a trench are undesirably removed from the trench. If the erosion becomes excessive, the electric resistance of the wirings would be increased, thereby degrading the performance of a semiconductor device. Additionally, there is also a possibility of generating the disconnection of wirings during the operation of large scale integrated circuits (LSI), thereby degrading the reliability of the semiconductor device. Therefore, it is required to control the size of the erosion to 20 nm or less.
It has been conventionally considered that the aforementioned requirement can be coped with by minimizing the generation of the free particles during the polishing, and hence, it has been conventionally proposed to employ a method to employ a fixed abrasive grain type CMP pad (for example, a fixed abrasive type CMP pad which is available from 3M Co., Ltd.) where the generation of free particles can be minimized. Although it may be possible to control the size of the erosion to not larger than 20 nm by using such a CMP pad, there are still left remained problems such as working efficiency, manufacturing cost, the quality of worked surface and the stability of products.
There is also proposed a method enhancing the interaction between abrasive grains and a polishing pad. For example, it is proposed to employ a slurry comprising composite particles as polishing grains, and an organic compound such as a surfactant or an organic acid. However, the employment of this slurry is impractical due to poor polishing efficiency thereof.